Home › Tools › Dog Age Calculator
Dog Age Calculator
How dog years work
The old "multiply by seven" rule fails because dogs mature quickly and then age more slowly, and because size changes everything. A Chihuahua routinely lives past 15, while a Great Dane is already a senior at 6. The chart used here follows the size-based conversion popularized by the AKC and AVMA: every dog is 15 human-equivalent years old at age one and 24 at age two. After that, each dog year adds 4 human years for toy/small breeds, 5 for medium, 6 for large and 7 for giant breeds.
A 2020 UC San Diego study offers a second lens. Working from DNA methylation in Labrador Retrievers, it derives a human-equivalent age of roughly 16 × ln(dog age) + 31. Both models agree that the first two dog years matter far more than any "×7" rule implies.
Conversion chart
| Dog age | Toy / Small | Medium | Large | Giant |
|---|---|---|---|---|
| 1 | 15 | 15 | 15 | 15 |
| 2 | 24 | 24 | 24 | 24 |
| 5 | 36 | 39 | 42 | 45 |
| 8 | 48 | 54 | 60 | 66 |
| 12 | 64 | 74 | 84 | 94 |
Sources: AKC dog age chart guidance; Wang et al., "Quantitative translation of dog-to-human aging by conserved remodeling of epigenetic networks" (Cell Systems, 2020).
Keep going
Frequently asked questions
How do I calculate my dog’s age in human years?
Use the size-based chart: 15 human years at dog age 1, 24 at age 2, then add 4–7 years per dog year depending on size class — toy adds 4, medium 5, large 6 and giant 7.
Why do small dogs live longer than large dogs?
Large and giant breeds age faster at the cellular level and carry higher cancer and joint disease risk, so a Chihuahua often reaches 15+ while a Great Dane’s typical lifespan is 7–10 years.
What is the epigenetic formula for dog years?
The UCSD 2020 study fit 16 × ln(dog age) + 31 to Labrador DNA methylation data. It is a useful cross-check but the size-based chart remains the practical standard.